A leading cause of mortality within the developed world is cardiovascular disease. Coronary disease is of most concern. Patients having such disease have narrowing in one or more coronary arteries. Generally, however, patients have narrowing in multiple coronary arteries. One treatment for the narrowing is stenting the blood vessel. Stenting involves the placement of a stent at the site of acute artery closure. This type of surgery has proved effective in restoring vessel patency and decreasing myocardial ischemia. However the exposure of currently used metallic stents to flowing blood can result in thrombus formation, smooth muscle cell proliferation and acute thrombotic occlusion of the stent.
Drug eluting stents (“DES”) generally result in lower restenosis and revascularization rates as compared to bare metal stents in vessels having a diameter greater than approximately 3.0 mm (“large vessels”). See, e.g., Ardissino D, et al., Sirolimus-eluting vs uncoated stents for prevention of restenosis in small coronary arteries: a randomized trial, JAMA, 2004. 292: p. 2727-34; Doucet, S., et al., Stent placement to prevent restenosis after angioplasty in small coronary arteries, Circulation, 2001. 104(17): p. 2029-33; Meier, B., et al., Sirolimus-eluting coronary stents in small vessels, Am Heart J, 2006. 151(5): p. 1019 e1-7; Stone, G. W., et al., Comparison of an everolimus-eluting stent and a paclitaxel-eluting stent in patients with coronary artery disease: a randomized trial, JAMA, 2008. 299(16): p. 1903-13. However, vessels having a diameter of less than or less than 3.0 mm (“small vessels”) continue to be clinically and angiographically at a disadvantage to larger vessels due to the inability of the small diameter to accommodate neointimal hyperplasia. See Godino, C., et al., Clinical and angiographic follow-up of small vessel lesions treated with paclitaxel-eluting stents (from the TRUE Registry), Am J Cardiol, 2008. 102(8): p. 1002-8. Various DES for treating small vessels having typical diameters of 2.25 mm, including the TAXUS® Atom, TAXUS® Liberte, Promus Element Stent, all three produced by Boston Scientific, Inc., the CYPHER®, produced by Johnson & Johnson, Inc. However, these small-vessel DES have not led to significantly reduced late loss diameter or percent diameter stenosis like their large-vessel DES counterparts. For example, for the core size Cypher used to treat vessels ≧2.5 mm to ≦3.5 mm, the 9 month in-stent late loss was 0.17 mm and 9 month in-stent restenosis rate was 3.2%. See Moses et al., “Sirolimus-eluting stents versus standard stents in patients with stenosis in a native coronary artery,” N. Engl. J. Med. 2003, 348:1315-23; Cypher IFU, Cordis Corporation 2010. Whereas for the 2.25 mm Cypher 6 month restenosis rate was much greater at 11.7%. See Moses J W, et al., “Safety and efficacy of the 2.25-mm sirolimus-eluting Bx Velocity stent in the treatment of patients with de novo native coronary artery lesions: the SIRIUS 2.25 trial,” American Journal of Cardiology 2006; 98(11):1455-1460. The core size Taxus Liberte used to treat vessels ≧2.5 mm to ≦4.0 mm had a 9 month in-stent late loss of 0.41 mm and in-stent restenosis rate of 11.38% and the 2.25 mm Taxus Liberte was associated with a higher restenosis rate of 13%. Even more dramatically the core size TAXUS Express stent, similar size to TAXUS Liberte, was associated with an in-stent restenosis rate of 8.64% at 9 months compared to a 9 month in-stent restenosis rate of 25.9%. See Stone G W et al., “Comparison of a polymer-based paclitaxel-eluting stent with a bare metal stent in patients with complex coronary artery disease: a randomized controlled trial,” Journal of the American Medical Association 2005; 294(10):1215-1223.
Without being held to any theory, it is believed that the difficulty in treating small vessels with drug eluting stents is that the narrow lumen of the smaller diameter vessels are more prone to revascularization. Thus, the stents configured to treat such vessels do not achieve similar positive results, for example, as measured by in-stent late loss, as the larger counterparts. Accordingly, there remains a need in the art for small-vessel DES that produce improved angiographic and clinical outcomes in small vessels.